1. Field of the Invention
The present invention relates to a fault determining apparatus for a data transmission system in a cyclic operating system and, particularly, to a diagnostic apparatus having an operation tracing memory.
2. Description of the Prior Art
In a conventional apparatus, some control parameters useful for diagnostic activity are registered in advance as trace information and this trace information along with detected faults for the latest few operating cycles is stored in a tracing memory so that it can be used for analyzing the faults. In such a conventional system, a parity error signal representing a faulty result of parity check is not included in the record of the tracing memory.
One major purpose of a parity check is to detect erroneous data occurring in the transmission system. However, in the absence of any parity error signal being stored in the tracing memory, no record of a fault in the data transmission system is obtained, and it is not known whether or not the data being traced is transmitted correctly. Therefore, the reliability of the traced data is unknown.